This is UniversalCoins, a mod made for Minecraft. It has been made open-source by its original creator, TED_996, in order to let the community update it to newer versions of Minecraft.

Original Minecraft Forum thread: http://www.minecraftforum.net/topic/1833251-162164 Browse here to understand the reasons for specific decisions, also to understand the way the mod works (and is supposed to work).

To edit the mod, dowload Minecraft Forge for Minecraft 1.6.4 and drop the files in /forge/mcp/src/minecraft. Use the standard modding processafter that.

1.6.2 versions of the mod can be found at the minecraftforum thread.

Unfortunately, the code is not commented (yet) but the names are hopefully descriptive.